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Human metapneumovirus: a newly emerging respiratory pathogen.

PURPOSE OF REVIEW: The present review focuses on the recent discovery, and clinical and epidemiological features of a virus associated with respiratory tract infections. RECENT FINDINGS: In June 2001, researchers in The Netherlands reported the discovery of a virus associated with respiratory tract disease in infants and children. Genetic studies of this newly discovered viral pathogen revealed that it was a paramyxovirus. This virus is the first human pathogen in the Genus Metapneumovirus and was called human metapneumovirus (hMPV). hMPV may be a common respiratory virus. Seroepidemiologic studies in The Netherlands suggested that, by age 5 years, nearly all individuals have been exposed to hMPV. The results of several studies suggest that hMPV may account for about 10% of respiratory tract infections in which a common respiratory virus, such as respiratory syncytial virus, or influenza or parainfluenza viruses, could not be detected. hMPV has been detected in patients with either upper or lower respiratory tract disease, or both. Symptoms associated with hMPV include cough, dyspnea, wheeze, and hypoxia. This newly recognized pathogen has been detected in children and adults. Epidemiological findings suggest that it may circulate worldwide and may have a seasonal distribution. SUMMARY: hMPV is a newly emerging respiratory pathogen and may be the cause of a significant proportion of both upper and lower respiratory tract infection in infants, children, and adults.

Adolescent↗

Evaluation of the role of respiratory viruses in acute myringitis in children less than two years of age.

BACKGROUND: The etiology of acute myringitis remains controversial although it is usually encountered in connection with acute otitis media (AOM). In most cases of acute myringitis a bacterial pathogen has been detected in the middle ear fluid, but the role of respiratory viruses has remained unclear. Our objective was to investigate the etiologic role of viruses in the pathogenesis of acute bullous and hemorrhagic myringitis in children <2 years of age. METHODS: A prospective longitudinal cohort study of 2028 children ages 7 to 24 months in primary care in the Finnish Otitis Media Vaccine Trial. Nasopharyngeal aspirate (NPA) and middle ear fluid (MEF) samples taken at the time of the diagnosis were examined by a time-resolved fluoroimmunoassay for antigen detection of adenoviruses; influenza viruses A and B; parainfluenza viruses 1, 2 and 3; and respiratory syncytial virus and by reverse transcription polymerase chain reaction for human rhinovirus and human enterovirus. RESULTS: Eighty-two children with bullous myringitis and 37 children with hemorrhagic myringitis were diagnosed during the 18-month follow-up period. In bullous myringitis a respiratory virus was detected in 70% of NPA samples and in 27% of MEF samples. In hemorrhagic myringitis 57% of NPA samples and 28% of MEF samples were virus-positive. The viral distribution was similar to that of AOM (virus positive 64% of NPA and 37% of MEF). CONCLUSIONS: We could not confirm any specific respiratory virus to be the etiologic agent in acute myringitis. The etiology of acute myringitis is similar to that of AOM in children <2 years of age.

Acute Disease↗

Raised levels of antibodies to human viruses at the clinical onset of autoimmune chronic active hepatitis.

Patients with autoimmune chronic active hepatitis (AICAH) often have very high titres of antibodies to rubella and/or measles virus. In the present study a young girl at the clinical onset of AICAH exhibited very high titres of antibodies against influenza viruses A and B, parainfluenza viruses, rubella virus and varicella-zoster virus. The titres normalized over 2 months except for rubella and varicella-zoster antibodies. Strong reactivities were seen against the rubella structural proteins E1, E2 and C in Western blot but IgM antibodies were not demonstrated. Total IgG was increased with normal ratios of subclasses. The IgG1 was the dominant antibody to E1 and E2, while IgG4 dominated the anti-C response. There was no significant shift in subclass reactivities over one year from onset. The polymerase chain reaction (PCR), using a nested primer set, was negative for rubella virus RNA in a liver biopsy obtained at the clinical onset and in peripheral blood mononuclear cells (PBMC) 1 year later. Co-cultivation experiments using PBMC and permissive cell lines were also negative for rubella virus. Hence, in the very early phase of AICAH there may be a transiently enhanced antibody response to various unrelated viruses.

Adolescent↗

Clinical manifestations of respiratory tract infections due to respiratory syncytial virus and rhinoviruses in hospitalized children.

From September 1984 to May 1986, nasopharyngeal secretions were obtained from 519 children with some form of respiratory tract infection. The nasal secretions were screened for respiratory syncytial virus (RSV), rhinoviruses, adenoviruses, parainfluenza virus types 1, 2, 3, influenza virus types A and B, and enteroviruses by tissue culture virus isolation technique and/or enzyme-linked immunosorbent assay. A uniform questionnaire gave information about age, sex, individual signs and symptoms, findings of the physical examination and clinical diagnosis of the patients. RSV was detected in 119 (23%) specimens and was thus the most frequent causative agent of respiratory infections. After RSV, rhinoviruses were the most frequently recovered pathogens accounting for 60 (12%) cases of acute respiratory disease. A comparison of the individual signs and symptoms, the findings of the physical examination and the clinical diagnosis of RSV and rhinovirus infected children revealed that there was no characteristic clinical pattern associated with either of the two viral respiratory pathogens. According to our results, rhinovirus infections were a major cause of lower respiratory tract infections in hospitalized children less than or equal to 3 years old.

Child, Preschool↗

Neonatal nosocomial respiratory infection with coronavirus: a prospective study in a neonatal intensive care unit.

The aim of this prospective study was to evaluate the incidence of viral respiratory infection in hospitalized premature newborn infants and to assess the role of coronaviruses. All hospitalized premature infants with a gestational age less than or equal to 32 weeks were included. Tracheal or nasopharyngal specimens were studied by immunofluorescence for coronaviruses, respiratory syncytial virus, adenoviruses, influenza and parainfluenza viruses. Forty premature infants were included; 13 samples were positive in 10 newborns (coronaviruses n = 10; influenza 1 n = 2; adenovirus n = 1). None was positive at admission. All premature infants infected with coronaviruses had symptoms of bradycardia, apnea, hypoxemia, fever or abdominal distension. Chest X-ray revealed diffuse infiltrates in two cases. However, no significant difference was observed between infected and non-infected premature infants for gestational age, birth weight, duration of ventilation, age at discharge, incidence of apnea or bradycardia. Nosocomial respiratory tract infection with coronaviruses appears to be frequent. The clinical consequences should be evaluated in a larger population.

Body Fluids↗

[The role of viral infection in adults with bronchopulmonary infections].

We isolated the virus from the respiratory specimens of 16 patients (7.9%) when we investigated the bronchopulmonary infections of 203 adult patients by the viral isolation method for the diagnosis of the viral infection and transtracheal aspiration (TTA) for taking directly the specimen from the lower respiratory tract. The bronchopulmonary infections, isolated the virus, consisted of acute bronchitis (3 cases), pneumonia (8 cases) and the acute exacerbation of chronic lower respiratory infection (5 cases). The positive viral isolation consisted of Rhinovirus (11 strains), Herpes simplex virus I (3 strains), Parainfluenza virus III (1 strain) and Respiratory syncytial virus (1 stain). There were 9 transtracheal aspirates, 8 pharyngeal swabs and 5 nasal washings in the positive viral specimens. We experienced 5 cases who had the same virus isolated from both the upper respiratory tract and the lower respiratory tract. H. influenzae, P. aeruginosa and other bacteria were found in 14 of the 16 TTA cultures. These results suggest that the role of the viral infection is important either independently or relating the bacterial infection in the adult bronchopulmonary infections.

Adult↗

Characterization of virus isolates by particle-associated nucleic acid PCR.

Diagnostic virus isolation is still frequently used, particularly from respiratory tract secretions. Testing positive virus cultures for all possible viruses is time-consuming, and unexpected or unknown viruses may escape detection. Therefore, a novel random PCR approach was developed that allows sequence-independent amplification of viral nucleic acids from virus isolation-positive cultures. Selectivity for viral sequences is obtained by preferential isolation of nucleic acids that are particle associated and resistant to nucleases. Using primers with a degenerated 3' end, the isolated nucleic acids are amplified and the randomly amplified PCR products are cloned and sequenced. As proof of the concept, the PAN-PCR approach was applied to supernatants of coxsackievirus B3 and murine adenovirus type 1-infected cells. Enterovirus and adenovirus sequences were obtained, demonstrating that the random PCR approach allows detection of RNA and DNA viruses. As a first application of this PAN-PCR approach, we characterized a virus isolate from mouth-washing material of a patient with chronic fatigue syndrome and high antibody titers to coxsackievirus B2. The virus isolate had tested negative for enteroviruses and respiratory viruses (influenza viruses A and B, parainfluenza virus types 1 to 3, respiratory syncytial virus, and adenovirus) by immunofluorescence and PCR. Particle-associated, nuclease-resistant RNA and DNA were prepared from the supernatant of infected cells. The DNA and the reverse-transcribed RNA were randomly amplified, and PCR products were cloned and sequenced. Of 25 sequences obtained from the DNA preparation, 24 contained herpes simplex virus type 1 (HSV-1) sequences from 14 different loci spread over the HSV-1 genome. This result was confirmed by using a standard diagnostic HSV-PCR, demonstrating that the PAN-PCR correctly identified the virus isolate. Although the identification of HSV-1 in mouth-washing material is not surprising in retrospect, it clearly demonstrates the applicability of the PAN-PCR approach. This method should be particularly useful for characterizing virus isolates that have tested negative for all expected viruses and for identifying unknown viruses.

Adenoviridae↗

Two nucleotides immediately upstream of the essential A6G3 slippery sequence modulate the pattern of G insertions during Sendai virus mRNA editing.

Editing of paramyxovirus P gene mRNAs occurs cotranscriptionally and functions to fuse an alternate downstream open reading frame to the N-terminal half of the P protein. G residues are inserted into a short G run contained within a larger purine run (AnGn) in this process, by a mechanism whereby the transcribing polymerase stutters (i.e., reads the same template cytosine more than once). Although Sendai virus (SeV) and bovine parainfluenza virus type 3 (bPIV3) are closely related, the G insertions in their P mRNAs are distributed differently. SeV predominantly inserts a single G residue within the G run of the sequence 5' AACAAAAAAGGG, whereas bPIV3 inserts one to six G's at roughly equal frequency within the sequence 5' AUUAAAAAAGGGG (differences are underlined). We have examined how the cis-acting editing sequence determines the number of G's inserted, both in a transfected cell system using minigenome analogues and by generating recombinant viruses. We found that the presence of four rather than three G's in the purine run did not affect the distribution of G insertions. However, when the underlined AC of the SeV sequence was replaced by the UU found in bPIV3, the editing phenotype from both the minigenome and the recombinant virus resembled that found in natural bPIV3 infections (i.e., a significant fraction of the mRNAs contained two to six G insertions). The two nucleotides located just upstream of the polypurine tract are thus key determinants of the editing phenotype of these viruses. Moreover, the minimum number of A residues that will promote SeV editing phenotype is six but can be reduced to five when the upstream AC is replaced by UU. A model for how the upstream dinucleotide controls the insertion phenotype is presented.

Base Sequence↗

Recombinant human Metapneumovirus lacking the small hydrophobic SH and/or attachment G glycoprotein: deletion of G yields a promising vaccine candidate.

Human metapneumovirus (HMPV) has recently been identified as a significant cause of serious respiratory tract disease in humans. In particular, the emerging information on the contribution of HMPV to pediatric respiratory tract disease suggests that it will be important to develop a vaccine against this virus for use in conjunction with those being developed for human respiratory syncytial virus and the human parainfluenza viruses. A recently described reverse genetic system (S. Biacchesi, M. H. Skiadopoulos, K. C. Tran, B. R. Murphy, P. L. Collins, and U. J. Buchholz, Virology 321:247-259, 2004) was used to generate recombinant HMPVs (rHMPVs) that lack the G gene, the SH gene, or both. The DeltaSH, DeltaG, and DeltaSH/G deletion mutants were readily recovered and were found to replicate efficiently during multicycle growth in cell culture. Thus, the SH and G proteins are not essential for growth in cell culture. Apart from the absence of the deleted protein(s), the virions produced by the gene deletion mutants were similar by protein yield and gel electrophoresis protein profile to wild-type HMPV. When administered intranasally to hamsters, the DeltaG and DeltaSH/G mutants replicated in both the upper and lower respiratory tracts, showing that HMPV containing F as the sole viral surface protein is competent for replication in vivo. However, both viruses were at least 40-fold and 600-fold restricted in replication in the lower and upper respiratory tract, respectively, compared to wild-type rHMPV. They also induced high titers of HMPV-neutralizing serum antibodies and conferred complete protection against replication of wild-type HMPV challenge virus in the lungs. Surprisingly, G is dispensable for protection, and the DeltaG and DeltaSH/G viruses represent promising vaccine candidates. In contrast, DeltaSH replicated somewhat more efficiently in hamster lungs compared to wild-type rHMPV (20-fold increase on day 5 postinfection). This indicates that SH is completely dispensable in vivo and that its deletion does not confer an attenuating effect, at least in this rodent model.

Animals↗

Acute viral infections of upper respiratory tract in elderly people living in the community: comparative, prospective, population based study of disease burden.

OBJECTIVE: To evaluate the disease burden of upper respiratory infections in elderly people living at home. DESIGN: Prospective surveillance of elderly people. INTERVENTION: None. SETTING: Leicestershire, England SUBJECTS: 533 subjects 60 to 90 years of age. MAIN OUTCOME MEASURES: Pathogens, symptoms, restriction of activity, duration of illness, medical consultations, interval between onset of illness and medical consultation, antibiotic use, admission to hospital, and death. RESULTS: 231 pathogens were identified for 211 (43%) of 497 episodes for which diagnostic specimens were available: 121 (52%) were rhinoviruses, 59 (26%) were coronaviruses, 22 (9.5%) were influenza A or B, 17 (7%) were respiratory syncytial virus, 7 (3%) were parainfluenza viruses, and 3 (1%) were Chlamydia species; an adenovirus and Mycoplasma pneumoniae caused one infection each. Infections occurred at a rate of 1.2 episodes per person per annum (95% confidence interval 1.0 to 1.7; range 0-10) and were clinically indistinguishable. Lower respiratory tract symptoms complicated 65% of upper respiratory infections and increased the medical consultation rate 2.4-fold (chi 2 test P < 0.001). The median interval between onset of illness and medical consultation was 3 days for influenza and 5 days for other infections. Rhinoviruses caused the greatest disease burden overall followed by episodes of unknown aetiology, coronaviruses, influenza A and B, and respiratory syncytial virus. CONCLUSIONS: Respiratory viruses cause substantial morbidity in elderly people. Although respiratory syncytial virus and influenza cause considerable individual morbidity, the burden of disease from rhinovirus infections and infections of unknown aetiology seems greater overall. The interval between onset of illness and consultation together with diagnostic difficulties raises concern regarding the role of antiviral drugs in treating influenza.

Aged↗